| Summary: | Background: We aimed to investigate how disc- and facet joint degeneration relate to ROM and spinopelvic alignment parameters. Their interrelation, however, is not yet understood, although eminent in patient specific modeling approaches and surgical decision making. Further is not yet sufficiently understood whether spinal alignment parameters relate to the degenerative states. Methods: The ROM of lumbar spinal segments was quantified using flexion/extension radiographs of 90 patients. The grades of degeneration of discs (IDD, Pfirrmann grades, n=440) and facet joints (FJD, Weishaupt classification, n=406) were assessed in CT and MRI scans. Results: The grade of IDD was significantly related to changes in ROM (p<0.01) whereas no association was observed with the amount of FJD. Grade V IDD was associated with a significant decrease in motion (p<0.01) compared to all other IDD grades (II-IV), which did not differ significantly among each other. The combined occurrence of IDD and FJD revealed the largest angular segmental ROM in segments with the lowest IDD (II) and lowest FJD (0). The lowermost ROM was present in fused segments (control), followed by those with severe IDD (V). In combination with FJD, the destabilizing effect of initial IDD was only observed if FJD was already in an advanced state. Conclusions: While the degree of facet joint degeneration seems not significantly associated with limitations in spinal motion, severe lumbar disc degeneration limits segmental motion, nearly equal to spinal fusion. This should affect counseling patients undergoing spinal fusion with questions on the probability of adjacent segment degeneration compared to the natural course.
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